1. Field of the Invention
The present invention relates to an image reading device and an image forming apparatus.
2. Description of the Related Art
In the related art, there is known a sheet-through type image reading device in which the sub-reading of the original image is performed by conveying the original to the reading position of the image reading unit in a sub-reading direction. If a foreign object such as dirt is attached to the reading surface of the image reading unit, this dirt generates a vertical stripe, which may significantly degrade the image.
In Japanese Patent No. 4477043, there is disclosed an image reading device configured to remove dirt attached to the reading surface by conveying the original such that the original makes contact with the reading surface of the image reading unit (image sensor). In the image reading device of Japanese Patent No. 4477043, the conveyed original makes contact with the reading surface of the image reading unit by configuring a pair of guide members including a guide member (hereinafter, referred to as an upper guide member) located in the image reading unit side with respect to the original conveying path provided in the upstream side of the original conveying direction from the image reading unit and a lower guide member arranged to face the upper guide member by interposing the original conveying path as follows. Specifically, a portion of the upper guide member in the downstream side of the original conveying direction is bent to the lower guide member side. In addition, a portion of the lower guide member in the downstream side of the original conveying direction from the bent portion of the upper guide member is bent to the image reading unit side. In such a configuration, the conveyed original is forcibly bent to the lower guide member side as the upper guide member bumps into the bent portion. Then, the original is forcibly bent to the image reading unit side as the lower guide member bumps into the bent portion, so that the original is conveyed to the upper direction, and the original can make contact with the reading surface of the image reading unit. As a result, the dirt attached to the reading surface of the image reading unit can be removed.
In the image reading device disclosed in Japanese Patent No. 4477043, since the original is conveyed while it is forcibly bent by making the original bump into each of the bent portions of the upper guide member and the lower guide member, a conveying force necessary to convey the original to the original reading unit increases. As a result, a size of the motor for conveying the original increases, and a size of the apparatus increases accordingly. In addition, as the size of the motor increases, it is necessary to increase rigidity of a portion for supporting the motor, which also increases costs. In addition, since each guide member conveys the original by forcibly bending the original using the bent portion, the position corresponding to the original, reading unit may be deviated depending on the thickness (stiffness) of the original, and the original may not make contact with the reading surface. Moreover, the dirt attached to the reading surface may not be appropriately removed depending on the thickness of the original.
Therefore, there is a need for an image reading device and an image forming apparatus capable of suppressing an original conveying force from increasing and suppressing a deviation of the position corresponding to the original reading unit depending on thickness (stiffness) of the original.